Abstract

We employ a Hodgkin-Huxley-type model of basolateral ionic currents in bullfrog saccular
hair cells for studying the genesis of spontaneous voltage oscillations and their
role in shaping the response of the hair cell to external mechanical stimuli. Consistent
with recent experimental reports, we find that the spontaneous dynamics of the model
can be categorized using conductance parameters of calcium-activated potassium, inward
rectifier potassium, and mechano-electrical transduction (MET) ionic currents. The
model is demonstrated for exhibiting a broad spectrum of autonomous rhythmic activity,
including periodic and quasi-periodic oscillations with two independent frequencies
as well as various regular and chaotic bursting patterns. Complex patterns of spontaneous
oscillations in the model emerge at small values of the conductance of Ca2+-activated potassium currents. These patterns are significantly affected by thermal
fluctuations of the MET current. We show that self-sustained regular voltage oscillations
lead to enhanced and sharply tuned sensitivity of the hair cell to weak mechanical
periodic stimuli. While regimes of chaotic oscillations are argued to result in poor
tuning to sinusoidal driving, chaotically oscillating cells do provide a high sensitivity
to low-frequency variations of external stimuli.